1 files changed, 107 insertions, 0 deletions
diff --git a/src/runtime/error.go b/src/runtime/error.go
new file mode 100644
index 000000000..0b40c702b
--- /dev/null
+++ b/src/runtime/error.go
@@ -0,0 +1,107 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime
+
+import "unsafe"
+
+// The Error interface identifies a run time error.
+type Error interface {
+	error
+
+	// RuntimeError is a no-op function but
+	// serves to distinguish types that are runtime
+	// errors from ordinary errors: a type is a
+	// runtime error if it has a RuntimeError method.
+	RuntimeError()
+}
+
+// A TypeAssertionError explains a failed type assertion.
+type TypeAssertionError struct {
+	interfaceString string
+	concreteString  string
+	assertedString  string
+	missingMethod   string // one method needed by Interface, missing from Concrete
+}
+
+func (*TypeAssertionError) RuntimeError() {}
+
+func (e *TypeAssertionError) Error() string {
+	inter := e.interfaceString
+	if inter == "" {
+		inter = "interface"
+	}
+	if e.concreteString == "" {
+		return "interface conversion: " + inter + " is nil, not " + e.assertedString
+	}
+	if e.missingMethod == "" {
+		return "interface conversion: " + inter + " is " + e.concreteString +
+			", not " + e.assertedString
+	}
+	return "interface conversion: " + e.concreteString + " is not " + e.assertedString +
+		": missing method " + e.missingMethod
+}
+
+// For calling from C.
+func newTypeAssertionError(ps1, ps2, ps3 *string, pmeth *string, ret *interface{}) {
+	var s1, s2, s3, meth string
+
+	if ps1 != nil {
+		s1 = *ps1
+	}
+	if ps2 != nil {
+		s2 = *ps2
+	}
+	if ps3 != nil {
+		s3 = *ps3
+	}
+	if pmeth != nil {
+		meth = *pmeth
+	}
+	*ret = &TypeAssertionError{s1, s2, s3, meth}
+}
+
+// An errorString represents a runtime error described by a single string.
+type errorString string
+
+func (e errorString) RuntimeError() {}
+
+func (e errorString) Error() string {
+	return "runtime error: " + string(e)
+}
+
+type stringer interface {
+	String() string
+}
+
+func typestring(x interface{}) string {
+	e := (*eface)(unsafe.Pointer(&x))
+	return *e._type._string
+}
+
+// For calling from C.
+// Prints an argument passed to panic.
+// There's room for arbitrary complexity here, but we keep it
+// simple and handle just a few important cases: int, string, and Stringer.
+func printany(i interface{}) {
+	switch v := i.(type) {
+	case nil:
+		print("nil")
+	case stringer:
+		print(v.String())
+	case error:
+		print(v.Error())
+	case int:
+		print(v)
+	case string:
+		print(v)
+	default:
+		print("(", typestring(i), ") ", i)
+	}
+}
+
+// called from generated code
+func panicwrap(pkg, typ, meth string) {
+	panic("value method " + pkg + "." + typ + "." + meth + " called using nil *" + typ + " pointer")
+}